Re: [PATCH -v3] ext4: refactor duplicated block placement code

[Eric Sandeen <sandeen@redhat.com>]

On 6/28/11 9:05 AM, Theodore Ts'o wrote:
> From: "Theodore Ts'o" <tytso@mit.edu>

I kind of wish you'd keep me on the From: even if you did
move the change to a new file.

Thanks,
-Eric

> I found that ext4_ext_find_goal() and ext4_find_near()
> share the same code for returning a coloured start block
> based on i_block_group.
> 
> We can refactor this into a common function so that they
> don't diverge in the future.
> 
> Thanks to adilger for suggesting the new function name.
> 
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
> ---
> 
> Moved new code to balloc.c, and rebased patch to take into account the
> fs/ext4/indirect.c reorganization.  -- Ted
> 
>  fs/ext4/balloc.c   |   48 ++++++++++++++++++++++++++++++++++++++++++++++++
>  fs/ext4/ext4.h     |    1 +
>  fs/ext4/extents.c  |   37 +------------------------------------
>  fs/ext4/indirect.c |   28 +---------------------------
>  4 files changed, 51 insertions(+), 63 deletions(-)
> 
> diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
> index 264f694..f8224ad 100644
> --- a/fs/ext4/balloc.c
> +++ b/fs/ext4/balloc.c
> @@ -620,3 +620,51 @@ unsigned long ext4_bg_num_gdb(struct super_block *sb, ext4_group_t group)
>  
>  }
>  
> +/**
> + *	ext4_inode_to_goal_block - return a hint for block allocation
> + *	@inode: inode for block allocation
> + *
> + *	Return the ideal location to start allocating blocks for a
> + *	newly created inode.
> + */
> +ext4_fsblk_t ext4_inode_to_goal_block(struct inode *inode)
> +{
> +	struct ext4_inode_info *ei = EXT4_I(inode);
> +	ext4_group_t block_group;
> +	ext4_grpblk_t colour;
> +	int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
> +	ext4_fsblk_t bg_start;
> +	ext4_fsblk_t last_block;
> +
> +	block_group = ei->i_block_group;
> +	if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
> +		/*
> +		 * If there are at least EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME
> +		 * block groups per flexgroup, reserve the first block
> +		 * group for directories and special files.  Regular
> +		 * files will start at the second block group.  This
> +		 * tends to speed up directory access and improves
> +		 * fsck times.
> +		 */
> +		block_group &= ~(flex_size-1);
> +		if (S_ISREG(inode->i_mode))
> +			block_group++;
> +	}
> +	bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
> +	last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
> +
> +	/*
> +	 * If we are doing delayed allocation, we don't need take
> +	 * colour into account.
> +	 */
> +	if (test_opt(inode->i_sb, DELALLOC))
> +		return bg_start;
> +
> +	if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
> +		colour = (current->pid % 16) *
> +			(EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
> +	else
> +		colour = (current->pid % 16) * ((last_block - bg_start) / 16);
> +	return bg_start + colour;
> +}
> +
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index ddaf504..49d2cea 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1743,6 +1743,7 @@ extern unsigned ext4_init_block_bitmap(struct super_block *sb,
>  				       struct ext4_group_desc *desc);
>  #define ext4_free_blocks_after_init(sb, group, desc)			\
>  		ext4_init_block_bitmap(sb, NULL, group, desc)
> +ext4_fsblk_t ext4_inode_to_goal_block(struct inode *);
>  
>  /* dir.c */
>  extern int __ext4_check_dir_entry(const char *, unsigned int, struct inode *,
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index eb63c7b..f331e50 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -114,12 +114,6 @@ static ext4_fsblk_t ext4_ext_find_goal(struct inode *inode,
>  			      struct ext4_ext_path *path,
>  			      ext4_lblk_t block)
>  {
> -	struct ext4_inode_info *ei = EXT4_I(inode);
> -	ext4_fsblk_t bg_start;
> -	ext4_fsblk_t last_block;
> -	ext4_grpblk_t colour;
> -	ext4_group_t block_group;
> -	int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
>  	int depth;
>  
>  	if (path) {
> @@ -161,36 +155,7 @@ static ext4_fsblk_t ext4_ext_find_goal(struct inode *inode,
>  	}
>  
>  	/* OK. use inode's group */
> -	block_group = ei->i_block_group;
> -	if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
> -		/*
> -		 * If there are at least EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME
> -		 * block groups per flexgroup, reserve the first block
> -		 * group for directories and special files.  Regular
> -		 * files will start at the second block group.  This
> -		 * tends to speed up directory access and improves
> -		 * fsck times.
> -		 */
> -		block_group &= ~(flex_size-1);
> -		if (S_ISREG(inode->i_mode))
> -			block_group++;
> -	}
> -	bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
> -	last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
> -
> -	/*
> -	 * If we are doing delayed allocation, we don't need take
> -	 * colour into account.
> -	 */
> -	if (test_opt(inode->i_sb, DELALLOC))
> -		return bg_start;
> -
> -	if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
> -		colour = (current->pid % 16) *
> -			(EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
> -	else
> -		colour = (current->pid % 16) * ((last_block - bg_start) / 16);
> -	return bg_start + colour + block;
> +	return ext4_inode_to_goal_block(inode);
>  }
>  
>  /*
> diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
> index c3e85a8..6c27111 100644
> --- a/fs/ext4/indirect.c
> +++ b/fs/ext4/indirect.c
> @@ -207,11 +207,6 @@ static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
>  	struct ext4_inode_info *ei = EXT4_I(inode);
>  	__le32 *start = ind->bh ? (__le32 *) ind->bh->b_data : ei->i_data;
>  	__le32 *p;
> -	ext4_fsblk_t bg_start;
> -	ext4_fsblk_t last_block;
> -	ext4_grpblk_t colour;
> -	ext4_group_t block_group;
> -	int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
>  
>  	/* Try to find previous block */
>  	for (p = ind->p - 1; p >= start; p--) {
> @@ -227,28 +222,7 @@ static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
>  	 * It is going to be referred to from the inode itself? OK, just put it
>  	 * into the same cylinder group then.
>  	 */
> -	block_group = ei->i_block_group;
> -	if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
> -		block_group &= ~(flex_size-1);
> -		if (S_ISREG(inode->i_mode))
> -			block_group++;
> -	}
> -	bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
> -	last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
> -
> -	/*
> -	 * If we are doing delayed allocation, we don't need take
> -	 * colour into account.
> -	 */
> -	if (test_opt(inode->i_sb, DELALLOC))
> -		return bg_start;
> -
> -	if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
> -		colour = (current->pid % 16) *
> -			(EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
> -	else
> -		colour = (current->pid % 16) * ((last_block - bg_start) / 16);
> -	return bg_start + colour;
> +	return ext4_inode_to_goal_block(inode);
>  }
>  
>  /**